Thomas Onslow, 2nd Earl of Onslow (15 March 1754 – 22 February 1827) was an English nobleman and courtier who succeeded to his title in 1814. Originally the Honourable Tom Onslow, he was styled Viscount Cranley from 1801 to 1814. He died in 1827 at his seat, Clandon Park in Surrey.
Onslow was born at Imber Court, Thames Ditton, Surrey, the eldest son of the then George Onslow.
On 30 December 1776, he married Arabella Mainwaring-Ellerker (d. 1782), by whom he had four children:
He subsequently married, on 13 February 1783, Charlotte Duncombe (d. 1819), née Hale, widow of Thomas Duncombe (d. 1779). They had one daughter:
Onslow entered the British House of Commons for Rye in 1775. In 1784, he left Rye and replaced his father's first cousin, Colonel Onslow, as MP for Guildford upon the retirement of the latter. He continued to represent that constituency until 1806, when he was replaced by his second son, Thomas Cranley.
A supporter of the Foxite Whigs, Onslow was, however, little active in the House of Commons, presenting a petition in 1781 on behalf of a "body of the innholders of England", complaining of the quartering of soldiers upon them. As an associate of the Prince, he was sent to Mrs Fitzherbert to tell her that the Prince had attempted suicide and only she could save his life, and he guarded the door of Fitzherbert's house when she secretly married the prince. However, he later fell out with the Prince, for reasons unknown, voting in favour of Pitt's regency proposal of 1789 and against the abolition of the slave trade in 1796.
Onslow was an amateur cricketer mainly associated with Surrey and he made 3 known appearances in first-class matches from 1801 to 1808.